Regulation of Energy Balance Flashcards
What percentage of energy expenditure does basal metabolic rate make up?
65-75%
What are the three ways which the body expends energy?
basal metabolic rate, activity (both spontaneous and voluntary), thermogenesis
What is the gold standard of measuring energy expenditure?
double labeled water - patient drinks water with oxygen 18 and deuterium and collect urine to look at outcomes
What is metabolism proportionate to?
body size
How is body weight maintained?
homeostasis - there is a set point
Do all subjects who are force fed gain the same amount of weight?
No
What correlates highly with the amount of fat gain due to force feeding?
activity thermogenesis (fidgeting)
Where in the brain is weight controlled?
the hypothalamus
What are the two types of neurons relating to weight in the arcuate nucleus?
NPY neurons and POMC neurons
Where do neurons in the arcuate nucleus project to?
the paraventricular hypothalamic nucleus and the lateral hypothalamus
What do NPY neurons secrete?
NPY and AGRP
What do NPY and AGRP promote?
eating
What do POMC neurons secrete?
MSH and CART
What receptor does MSH bind to?
MC4
What do MSH and CART inhibit?
food intake
What hormones are released by the paraventricular hypothalamic nucleus?
oxytocin and CRH
What do oxytocin and CRH inhibit?
food intake
What hormones are released by the lateral hypothalamus?
orexin and MCH
What do orexin and MCH promote?
food intake
Where else does the paraventricular hypothalamic nucleus and lateral hypothalamus get input from?
Vagus nerve
What modulates the system?
opioids, dopamine and endocannabinoids
What else provides peripheral modulation of the system?
higher cortical centres (conscious will), the size of fat stores and the presence of food in the gut
What is leptin?
A peptide hormone made in fat cells in proportion to the size of the cell that travels to the brain and is a powerful inhibitor of food intake
What is insulin?
A peripheral signal that is a long term inhibitor of food intake
How are nutrients involved in food intake control?
Can inhibit food intake
How does glucose inhibit food intake?
glucose metabolism leads to the production of malonyl-CoA which inhibits CPT1 preventing the breakdown of LCFA-CoA which inhibits food intake
What genes determine obesity?
leptin, leptin receptor, POMC, prohormone covertase 1, MC4R
What explains the increase in prevalence of obesity?
epigenitics
What are causes of spontaneous weight loss?
endocrine diseases, gastrointestinal diseases, infection, malignancy, anorexia nervosa
